Ion-Pair LC Analysis of Pyrroloquinoline Quinone in Neurotransmitter Amino Acid Incubations: Determination of Chemical Kinetics

Neurotransmitters are the chemical messengers of the brain. Many neurodegenerative diseases of the central nervous system are related to abnormal neurotransmitter activity. Pyrroloquinoline quinine (PQQ) has previously been shown to be a promising candidate for preventing cognitive deficit in neurodegeneration. To investigate whether PQQ can modulate the levels of brain neurotransmitter amino acids, a rapid and reliable ion-pair liquid chromatographic method was established and validated for the analysis of PQQ in reaction mixtures containing specific neurotransmitter amino acids. The reaction mixtures were separated on an amethyst C18-P reverse-phase column with 35:65 (v/v) acetonitrile:20 mM potassium dihydrogen phosphate, pH 5.5, containing 20 mM tetrabutyl ammonium bromide as mobile phase at a flow rate of 0.8 mL min⁻¹. The validated method was applied successfully to study the chemical kinetics of PQQ reactions with five neurotransmitter amino acids. Order of reaction n, rate constant k, and activation energy E _a values for the reactions were calculated. This work provides important information for studying the possible protective mechanisms of PQQ in neurodegenerative diseases. Furthermore, the simplicity of this method combined with its sensitivity and reliability make it a novel contribution in the field of neurotransmitter research.

     

液相色谱-质谱联用技术结合多探针底物法研究人参皂苷Rb1的体外代谢

以奥美拉唑、 苯妥英、 卡马西平和非那西丁为检测肝药酶细胞色素P450酶(CYP450)亚型的专属探针药物, 通过原型药物减少量测定法考察药物体外代谢的变化, 评价人参皂苷Rb1对CYP450不同亚型酶的作用. 结果表明, P2C9, P2C19和P3A4实验组与对照组差异不显著, P1A2实验组与对照组差异显著, 表明人参皂苷Rb1能诱导P1A2亚型酶的活性, 促进底物与酶反应, 加快底物的代谢, 而对P2C9, P2C19和P3A4三个亚型酶有弱的诱导或无诱导作用. 根据快速分离液相色谱-质谱联用(RRLC-MS/MS)检测结果推断, 人参皂苷Rb1在CYP450酶中的代谢产物可转化为人参皂苷Rb1氧化产物(Rb1+O)及人参皂苷Rd和F2.     

Ion-Pair LC Method for Simultaneous Determination of Aliskiren Hemifumarate,Amlodipine Besylate and Hydrochlorothiazide in Pharmaceuticals

A rapid and precise LC method was developed for the simultaneous determination of aliskiren hemifumarate (ALS), amlodipine besylate (AML) and hydrochlorothiazide (HCZ) using acetonitrile:25 mM octane sulfonic acid sodium salt monohydrate in water (60:40 v/v) as the mobile phase. The flow rate was maintained at 1.2 mL min^?1 on a stationary phase composed of Supelco, Discovery^® HS (C18) column (25 cm × 4.6 mm, 5 μm). Isocratic elution was applied throughout the analysis. Detection was carried out at λ _max (232 nm) at ambient temperature. The method was validated according to ICH guidelines. Linearity, accuracy and precision were satisfactory over the concentration ranges of 32–320, 2–44 and 4–64 μg mL^?1 for ALS, AML and HCZ, respectively. LOD and LOQ were estimated and found to be 0.855 and 2.951 μg mL^?1, respectively, for ALS, 0.061 and 0.202 μg mL^?1, respectively, for AML as well as 0.052 and 0.174 μg mL^?1, respectively, for HCZ. The method was successfully applied for the determination of the three drugs in their co-formulated tablets. The results were compared statistically with reference methods and no significant difference was found. The developed method is specific and accurate for the quality control and routine analysis of the cited drugs in pharmaceutical preparations.     

离子对色谱法测定麻杏石甘汤中的麻黄碱和伪麻黄碱

麻杏石甘汤出自《伤寒论》,由麻黄、杏仁、甘草和石膏四味中药组成。麻黄主要含麻黄碱和伪麻黄碱,两者是麻杏石甘汤中的主要有效成分。对麻黄及其制剂中的麻黄碱和伪麻黄碱含量测定的方法主要有高效液相色谱法（HPLC）、高效毛细管电泳法和气相色谱-质谱联用法等。由于麻黄碱和伪麻黄碱结构相似,而且生物碱容易产生拖尾现象,采用反相高效液相色谱法一般难以使两者达到良好的分离。本文采用反相离子对HPLC使两者获得了良好的分离,并以此法对麻杏石甘汤中的麻黄碱和伪麻黄碱进行了测定。     

不同条件下离体大鼠肝脏线粒体能量代谢微量热分析

为了探究线粒体的能量代谢过程,本文以离体大鼠肝脏线粒体为模型,利用多通道、高灵敏度的热活性检测仪TAM Ⅲ,实时监测了不同线粒体浓度、不同底物、不同缓冲液、几种呼吸抑制剂以及Ca²⁺和线粒体渗透转换孔抑制剂CsA存在时线粒体的能量代谢,获得了完整的热功率―时间曲线,并通过计算得到了线粒体能量代谢的热动力学参数。通过分析发现：（1）线粒体浓度越大,代谢越快;（2）直接底物琥珀酸钠使线粒体代谢更快;（3）高浓度Ca²⁺能够刺激线粒体快速产热,且在长期代谢进程中,线粒体渗透转换孔抑制剂CsA并不能改变Ca²⁺造成的影响;（4）不同缓冲液对线粒体代谢的影响基于其组分的不同,缓冲液中含有呼吸底物;（5）呼吸抑制剂都能抑制线粒体的能量代谢,尤其是复合物IV的抑制剂NaN₃,高浓度下使代谢停止。     

Use of A New HPLC Method in Rat Liver Microsomal Testosterone Monooxygenation and Its Application to Study the Sex Dependent Expression of Several Hydroxylases

Abstract

An HPLC method described by Mancilla and Gil [Analytical Letters 17, (B9), 1984, 873-886] has been applied to study the sex dependent expression of several rat liver testosterone hydroxylases. A sample clean up procedure has been developed using SEP-PACK C- 18 cartridges which retained testosterone and its microsomal oxidative products. Undesired components were not retained or selectivly eluted with organic solvents. The clean steroid sample was eluted with a mixture of n-hexane and 2-propanol. HPLC of testosterone microsomal oxidation products was performed by normal phase In a Lichrosorb diol column using an Isocratic mixture of n-hexane and 2-propanol. The main five testosterone metabolites produced by male and female rat liver microsomes were determined In only 24 min. The turnover rates for testosterone oxidation were similar in male and female microsomes, but significant differences were observed in the rate of production of different metabolites. Male microsomes catalized mainly oxidation at positions 2 α, and 7 α; whereas female microsomes produced mainly 7 α OHT and androstenedione. These results might be explained by the different contribution of some cytochrome P-450 isozymes in microsomes from the different sexes. This method provides a useful tool to study the P-450 isozymic contributions to microsomal activities in different tissues and might facilitate the comparison of P-450 isozymes purified in different laboratories.     

Photomodulation of Oxidative Metabolism and Electron Chain Enzymes in Rat Liver Mitochondria

Abstract— Low-level laser irradiation has been applied in a variety of laboratory studies and clinical trials for photobiostimulation over the last three decades. Considerable skepticism exists regarding the concept of photostimulation within the medical community. One of the major difficulties with photoirradiation research is that it lacks experimentally supportable mechanisms for the alleged photobiostimulatory effects. This study was undertaken to determine whether oxidative metabolism and electron chain enzymes in rat liver mitochondria can be modulated by photoirradiation. Oxygen consumption, phosphate potential, and energy charge of rat liver mitochondria were determined following photoirradiation. Activities of mitochondrial enzymes were analyzed to assess the specific enzymes that are directly involved with the photostimulatory process. An argon-dye laser at a wavelength of 660 nm and at a power density of 10 mW/cm² was used as a photon source. Photoirradiation significantly increased oxygen consumption (0.6 J/cm² and 1.2 J/cm², P < 0.05), phosphate potential, and the energy charge (1.8 J/cm² and 2.4 J/cm², P < 0.05) of rat liver mitochondria and enhanced the activities of NADH: ubiquinone oxidoreductase, ubiquinol: ferricytochrome C oxidoreductase and ferrocytochrome C: oxygen oxidoreductase (0.6 J/cm², 1.2 J/cm², 2.4 J/cm² and 4.8 J/cm², P < 0.05). The activities of succinate ubiquinone oxidoreductase, ATPase, and lactate dehydrogenase were not affected by photoirradiation.     

Dietary Vitamin B6 and Enzymes of Methionine Metabolism in Rat Liver

Hepatic cystathionase activity, but not methionine adenosyl-transterase and cystathionine synthetase, was markedly decreased in weanling female rats fed a vitamin B₆-deficient diet, compared to that of the control animals fed ad libitum or pair-fed. The depressed enzyme activity was restored rapidly to normal by administering pyridoxine to the deficient rats. Excess pyridoxal phosphate added to enzyme reaction mixtures stimulated cystathionase in liver extracts from both control and deficient animals, but it did not raise activity of deficients to normal level. The data indicate that the amount of apocystathionase in rat liver is regulated by the availability of its coenzyme vitamin.     

高效液相色谱法同时测定双酚伪麻干混悬剂中的盐酸伪麻黄碱和氢溴酸右美沙芬

建立了可同时测定双酚伪麻干混悬剂中盐酸伪麻黄碱和氢溴酸右美沙芬含量的反相高效液相色谱方法。样品先经甲醇溶解,过滤,然后以Lichrospher C6H6化学键合硅胶为固定相、乙腈-水-H3PO4（体积比为50∶50∶0.1,pH 2.5,内含1 g/L十二烷基硫酸钠)为流动相进行色谱分离,在220 nm处定量测定。结果表明,氢溴酸右美沙芬、盐酸伪麻黄碱的质量浓度分别为1.03~206 mg/L和5~200 mg/L时,其峰面积与质量浓度的线性关系良好;批内(n=7)测定的平均相对标准偏差（RSD）分别为1.8%和1.0%,批间(n=5)测定的RSD分别为2.2%和1.5%;对双酚伪麻干混悬剂中氢溴酸右美沙芬、盐酸伪麻黄碱测定回收率分别为100.0%~101.8%和95.7%~98.7%。该法适用于双酚伪麻干混悬剂中氢溴酸右美沙芬和盐酸伪麻黄碱的质量控制及含量测定,方法准确,操作简便。     

LC Determination of Icariside II in Rat Plasma and Tissues: Application to a Tissue Distribution Study

A sensitive and reliable reversed-phase liquid chromatography (RP-LC) with ultraviolet (UV) detection has been developed and validated for the quantification of Icariside II in rat plasma and tissues using Fermononetin as the internal standard. Protein precipitation and liquid?Cliquid extraction were utilized for plasma and tissue sample preparation, respectively. The analysis was successfully carried out on an Agilent SB-C₁₈ column (5 ??m, 4.6 × 250 mm) with the implementation of the following conditions: a mobile phase of phosphoric acid solution (0.1%, v/w)?CAcetonitrile (55:45, v/v), a flow rate of 1 mL min^?1, a column temperature of 25 °C and a detection wavelength of 270 nm. Good linear relationships of calibration curves were obtained (r ² > 0.9906) over the investigated concentration range with plasma and tissue samples. The lower limit of quantification (LLOQ) and the limit of detection (LOD) were 0.1 and 0.02 ??g g^?1, respectively (for plasma sample, they were 0.05 and 0.1 ??g mL^?1, respectively). The developed method which was embodied with good precision, accuracy, recovery and stability was corroborated to satisfy the requirements for biomedical sample analysis. This method has been successfully applied to tissue distribution study of Icariside II in rats after a single intravenous dose at 12.5 mg kg^?1. Results suggested that Icariside II was distributed to rat tissues rapidly with greater initial concentrations in kidney, lung and liver. Moderate initial distributions were obtained in rat muscle, heart, bone, spleen and plasma. Low amount of Icariside II was detected in testes, and no Icariside II could be detected in the brain.     

Simultaneous LC Analysis of Food Dyes in Soft Drinks

Liquid chromatography with diode-array detection has been used for simultaneous analysis of eight water-soluble synthetic colorants (E102, E104, E110, E122, E124, E129, E131, and E133) in non-alcoholic beverages. The colors were separated in 15 min on a C₁₈ reversed-phase column with a linear mobile phase gradient prepared from tetrabutylammonium hydrogen sulfate, methanol, and deionized water. The analytical characteristics of the separation were evaluated. Good linearity (r ² = 0.9988–0.9999), adequate limits of quantification, and high recovery (from 96.3 to 98.5%) were achieved. The method was used for analysis of 57 samples of soft drinks. The experimental results showed the colorants were present in 34 of the samples, and confirmed the method is sensitive, rapid, precise, and suitable for routine analysis of synthetic organic dyes.

     

LC Determination of Amino Acids in Rat Plasma with Fluorescence Detection: Application to Exercise Physiology

An LC method for the determination of 20 amino acids (AAs), using 1,2-Benzo-3,4-dihydrocarbazole-9-ethyl chloroformate (BCEOC) as fluorescent labeling reagent, has been validated and applied for the analysis of AAs in rat plasma at three different states concerning exercise physiology. Identification of AA derivatives was carried out by LC-MS with electrospray ion (ESI), and the MS-MS cleavage mode of the representative tyrosine (Tyr) derivative was analyzed. Gradient elution on a Hypersil BDS C₁₈ column gave good separation of the derivatives. Excellent linear responses were observed and good compositional data could be obtained from as little as 50–200 μL of plasma samples. The contents of 20 AAs in rat plasma of three groups (24 rats, group A: quiet state, group B: at exercising exhaust, group C: 12 h after exercising exhaust) exhibited evident difference corresponding to the physiological states. Facile BCEOC derivatization coupled with LC-FLD-ESI-MS analysis allowed the development of a highly sensitive method for the quantitative analysis of trace level of AAs from plasma or other biochemical samples.     

中空纤维液-液-液微萃取/HPLC分析人尿液中麻黄碱及伪麻黄碱

建立了中空纤维液-液-液微萃取高效液相色谱对人尿液中的麻黄碱和伪麻黄碱进行纯化、分离、富集以及测定的方法。采用中空纤维三相微萃取装置,考察了影响萃取的因素,确定了萃取条件:中空纤维壁上的有机相为正辛醇,以50μL盐酸溶液(pH 2.0)为接受相,在室温下萃取60 min。该条件下麻黄碱和伪麻黄碱的富集倍数分别为180倍和220倍,两者的线性范围分别为0.01～5 mg/L和0.005～0.75 mg/L,相关系数(r)分别为0.998 2、0.997 8,定量下限分别为0.01、0.005 mg/L。该方法使用极少量的有机溶剂,便可有效地对尿样中麻黄碱和伪麻黄碱进行纯化、分离和富集,萃取效率高,可用于尿液中麻黄碱和伪麻黄碱的同时测定。     

High Performance Liquid Chromatography Determination of Chlorpropham and Its Metabolites in Isolated Rat Hepatocyte Incubations

Abstract

Free chlorpropham (CIPC) and its metabolites (4-hydroxy CIPC, 3-chloroani-line and 3-chloroacetanilide) were separated by reverse phase high performance liquid chromatography (H.P.L.C.) using an isocratic procedure. The separation was used to quantify the metabolism of CIPC in rat hepatocyte incubations. The free metabolites were diethylether-extracted at pH 7.4. The sulfate and glucuronide conjugates of 4(OH)CIPC were enzymatically split and the aglycone determined by HPLC. Beside the unmetabolized CIPC which accounts for 33% of the dose, 4(OH)CIPC as the sulfoconjugate and glucuroconjugate represents 35% and 20% respectively, while free 4(OH)CIPC accounts for only 3%. About 10% of the CIPC is hydrolytically split yielding 3-chloroaniline (2%) which further transformed into 3-chloroacetanilide (5%).

In spite of the great sensitivity of the proposed method (0.2 μg/ml incubation medium) no other metabolites were recorded. This extraction and separation procedure could be applicable to future metabolic studies in cellular incubation systems.     

LC Method for Quantification of Lutein in Rat Plasma: Validation, and Application to a Pharmacokinetic Study

A reversed-phase LC method has been developed for quantitative analysis of lutein in rat plasma and applied to a study of the pharmacokinetics of lutein in rats. From a variety of compounds and solvents tested, astaxanthin was selected as the internal standard. n-Hexane was found to be the best solvent for extracting lutein from plasma. LC analysis of the extracts was performed on a C₁₈ column equipped with a guard pre-column. Linearity was good (r > 0.99) over the range 10–100 ng mL^?1. Recovery from plasma was 82.7–92.9% the intra-day and inter-day precision were always better than 3%. The limits of detection (LOD) and quantification (LOQ) were 2.5 and 8.3 ng mL^?1, respectively. The LC method was used to quantify lutein and zeaxanthin in rat plasma in a 36-h pharmacokinetic study in which experimental rats received a single oral dose of lutein (20 mg kg^?1). The results are presented.     

毛细管电泳/发光二极管诱导荧光法测定麻黄中麻黄碱与伪麻黄碱含量

基于麻黄碱及伪麻黄碱衍生物的光谱及化学性质,设计并构建了毛细管电泳/发光二极管诱导荧光检测系统.对关键光学元件进行组合选择,以蓝光发光二极管为光源,BP 470和BP 530分别为光源滤光片和荧光滤光片,光电倍增管检测信号,并对电泳分离系统的缓冲溶液、分离电压等参数进行优化;以FITC为衍生试剂,10 mmol/L Na2B4O7+ 16 mmol/L SDS为缓冲溶液,12 kV电压下可实现麻黄中麻黄碱和伪麻黄碱的基线分离.在0.25～10 mg/L范围内,麻黄碱和伪麻黄碱标准溶液的质量浓度与荧光响应的峰高之间呈较好的线性关系,相关系数(r)均大于0.99,其检出限分别为0.38 μg/L和0.29 μg/L,峰高的日内重复性(RSD)分别为2.0％和2.2％,日间重复性(RSD)分别为5.4％和5.1％.将该方法用于中药麻黄中麻黄碱和伪麻黄碱的测定,加标回收率分别为94％和107％.     

离子对试剂及其在多肽及蛋白质分离分析中的应用

离子对试剂是实现反相离子对色谱(Reversed-phase Ion-pair Chromatography,RPIC)快速灵敏和高分辨的关键因素.离子对试剂的正确选择和适当的添加,对多肽及蛋白质的分离分析有着显著影响.本文介绍了RPIC的基本原理及其在蛋白多肽分析中的应用前景,并详细阐述了常用离子对试剂的种类、特点及...     

The Analysis of Enantiomeric and Diastereoisomeric Mixtures of Ephedrine and Pseudoephedrine Using Reversed-Phase High Performance Liquid Chromatography of Nickel Dithiocarbamate Complexes

Abstract

Following their conversion to dithiocarbamate ligands and thence to nickel complexes, enantiomeric mixtures of ephedrine or pseudoephedrine may be separated and quantitated by reversed-phase High Performance Liquid Chromatography (HPLC) using ternary solvent mixtures. The solvent used to dissolve the complexes prior to injection was found to have a significant effect on the separation. In a similar manner, a mixture of the diastereoisomers ephedrine and pseudoephedrine was separated and quantitatively analysed using a binary solvent as the mobile phase. This separation was achieved both with prior formation of the nickel complexes and also with on-column formation using nickel(II) ions in the mobile phase. The analysis of diastereoisomeric contaminants in pharmaceutical products and raw materials containing ephedrine or pseudoephedrine is illustrated.     

大鼠肝过氧化物酶体中脂肪酸的分析

 用双 (2 乙基己基 )酚酞酸酯 (DEHP)诱导大鼠肝过氧化物酶体增殖 ,再用蔗糖密度梯度离心法分离大鼠肝细胞过氧化物酶体 ,并用十七烷酸作内标 ,以毛细管气相色谱法在非极性SPB 1石英毛细管柱上对其中的 11种脂肪酸进行分离测定。正常组和诱导组的大鼠肝过氧化物酶体中的不饱和脂肪酸和长链脂肪酸所占总脂肪酸的比例及总脂肪酸的统计结果是 :诱导组的不饱和脂肪酸的含量高于正常组的 (P <0 0 5 ) ,而两个组的脂肪酸总量及长链脂肪酸的含量无明显差别。结果提示 :诱导组的大鼠肝过氧化物酶体的脂肪酸成分发生了变化 ,其膜结构与正常组的不相同。     

Simultaneous Quantification of Anandamide and Other Endocannabinoids in Dorsal Vagal Complex of Rat Brainstem by LC–MS

A quantitative method has been developed and validated for the simultaneous determination of anandamide (AEA), docosatetraenylethanolamide (DEA) and N-arachidonyldopamine (NADA) in dorsal vagal complex (DVC) of rat brainstem by liquid chromatographic-electrospray ionization mass spectrometry. The analytes were extracted from the tissue samples of rat brainstem by a single step liquid extraction technique using acetonitrile. The chromatographic separation was conducted on a C18 column using a gradient mobile phase consisting of methanol and water at a flow rate of 0.3 mL min^?1. The analytes were quantified by positive electrospray ionization mass spectrometry with selected ion monitoring (SIM) mode. The limits of detection (LOD) for AEA, DEA and NADA were 0.5, 1 and 0.5 ng mL^?1, respectively. This method required only simple processing of the samples and could be applied to monitor the change in the level of these compounds in DVC of the rat brain tissue. Time dependent (10–70 min) accumulation of the endocannabinoids (AEA, DEA, and NADA) in brain tissue was also studied, which included a novel examination of the accumulation of DEA as a function of time in rat brain tissue after decapitation.